Coating materials of the prior art, which are used to give thermal resistance, corrosion resistance and electrical characteristics (insulating properties, low dielectric properties, etc.) to metal materials, inorganic materials and electronic material substrates, consist primarily of those made from polyorganosiloxane resin (silicone resin).
More recently, research has been conducted on a film originating in polyorganosiloxane in which the structure is controlled in the form of a low dielectric material for use as a semiconductor interlayer insulating film.
Although ceramic films of the prior art originating in polyorganosiloxane exhibit low specific dielectric constants on the order of 2.7-3.0, as the firing temperature increases, the specific dielectric constant also tends to increase. For example, in polyorganosiloxane having a methyl group in its side chain, thermal cleavage of the Si--Me group occurs at about 350.degree. C., and SiO.sub.2 formation progresses remarkably at high temperatures of 400.degree. C. and above. Thus, the dielectric constant increases as film density rises. In addition, since contraction of the film occurs as SiO.sub.2 formation progresses, cracking and other problems occur.
Since heat at a maximum of about 450.degree. C. is applied in the semiconductor production process, there was a problem with the thermal resistance even in the case of conventional siloxane-based polymers.
Accompanying the growing use of ICs featuring higher levels of integration and higher processing speeds, these coating materials, and semiconductor interlayer insulating films in particular, are being required to demonstrate even lower dielectric constants.
Polysiloxazane produced by a complexing method using halosilane and ammonia is described in Japanese Examined Patent Publication No. 6-18885 (Japanese Patent No. 1897366) filed by the present applicant. However, there is no description of polyorganosiloxazane containing organic groups in substantially all of its repeating units. In addition, said polysiloxazane is a polymer for producing silicon oxynitride fibers, and there have been no studies conducted whatsoever on the dielectric constant of that formed into a ceramic material.
The object of the present invention is to provide a precursor polymer that allows a ceramic material to be obtained that exhibits a low specific dielectric constant of, for example, 2.7 or less, even in the case of being treated at high temperatures of, for example, 400.degree. C. and above. Another object of the present invention is to provide a precursor polymer that allows control of this specific dielectric constant.